1. Field of the Invention
The present invention relates generally to a hinge fitting for pivotally connecting the back of a seat at both sides thereof to the seat frame, particularly of an automobile or other vehicle, and more particularly to a releasable locking device combined with such a fitting for adjusting the degree of inclination of the back relative to the seat by means of a gear or gear sector which is associated with one part of the fitting and a pawl which is associated with the other part and adapted to engage the gear at different angular positions of the back relative to the seat.
2. Description of the Prior Art
Fittings of this type are usually provided in pairs with their two parts secured to the seat and to the back, respectively, and at each side thereof, and the two parts of each fitting are pivotably connected by a pin which otherwise serves as the swivel axis for tilting the back forwardly or rearwardly. The fittings are secured at each side of the seat in such a manner that the pins thereof are in aligned relation with each other and positioned parallel with and near the rear edge of the seat to pivot the back to the seat.
In such devices, the possibility always exists of ruining the mechanism because of shock resulting from a sudden stop of the forward travel of the vehicle, causing a passenger in the rear passenger seat of the vehicle to strike the back of the seat under considerable inertial force, unless provision is made to overcome any dangerous overloading that may be applied to the back rest by a passenger in the rear passenger seat.
In order to safeguard the mechanism against excessive stress being exerted by such overloads, and resulting breakage, the distance between the center of the pin and the teeth of the gear or gear sector may beneficially be enlarged in design. It should be noted that, for a given load, the stress exerted is inversely proportional to such distance, so that the greater the distance, the smaller will be the stress. However, larger distances necessitate enlargement of the size of the sector gear, but large size sector gears will provide an obstruction for a passenger every time he has to leave the seat. This is a shortcoming in the practice of known hinge fittings for seats with movable backs.